1. Field of the Invention
The present invention relates to artificial insemination of bovines and other animals.
2. Description of Related Art
Worldwide, artificial insemination (AI) has penetrated about 80% of the dairy industry but only about 5% of the beef producing industry. One reason is the need for skilled personnel, veterinarians and technicians, trained to grasp the cervix via the rectum and to guide the AI pipette into or through the cervix.
In the traditional method, the inseminator must learn to insert the insemination tube into the cervix by developing the tactile skill to work through the wall of the large intestine while pushing the tube forward through the vagina with the other hand. The cervix is a number of inches long (4-6" in beef cattle), and sometimes has several bends (e.g. "s" or "v" shape in some Brahman cattle), and has several very tight sphincters through which the tube must be guided. Hence there is the ever present danger of perforating the wall of the cervix or the uterus with the inseminating tube, causing injury to the animal. Because of these difficulties, it is often impossible to advance the inseminating tube very far into the cervix, with a corresponding lower insemination efficiency and conception success rate.
For these reasons it normally takes five to six days and two to three cows on which to practice in order to gain an initial skill level. Relatively few who attempt to learn develop a high level of proficiency. Often the practice cows are ruined and must be slaughtered. Also the traditional method of manipulation of the cervix through the large intestine is only practical in large animals such as bovines where the intestine is large enough to be able to introduce the hand and arm. There is no comparable method for small animals such as sheep or goats.
U.S. Pat. No. 5,147,299 to Mendoza et al. describes a device to facilitate the artificial insemination of bovines and other animals. The device allows unskilled persons to learn intracervical semen deposition quickly and effectively without involving rectal penetration and any manipulation of the cervix. The device is inserted into the cervix using a simple illuminated vaginal speculum made of plastic which allows visualization of the cervical opening.
An ordinary inseminating pipette, through which semen is introduced using a syringe, is inserted into one end of a tube which has ejection ports at the other end. A sealing device, e.g. an inflatable balloon, is attached to the side of the tube. The tip is inserted into the cervix, under sight through the speculum, until most of the balloon has disappeared. The balloon is then inflated, forming a seal and anchoring the AI pipette, and semen is injected into the uterus.
While the device has been a great advancement in artificial insemination, reducing time, expenses and effort, and increasing effectiveness, there are still a number of problems. One problem is that the device does not deliver the optimum quantity and concentration of semen that will maximize the probability of conception since there is no way to assure that all of the semen is transferred from its strorage straw into the uterus of the animal without any losses. Another problem is that the device does not make it simple to deliver the optimum total charge of semen and diluting fluid required to accomodate the cervixes and uteruses of animals of varying sizes since there is no way to vary the total charge while preserving the optimum quantity and concentration of semen.
In operation, the frozen semen sample in a common plastic semen storage straw (a plastic tube sealed at both ends containing the semen sample, and stored in a dewar of liquid nitrogen) is warmed and mixed with diluting fluid contained in an ampule. The diluted semen is then loaded into the inseminating pipette by aspirating it out of the ampule, whereupon it is pushed with air from a syringe out of the distal end of the pipette into the uterus of the animal through the anchored tip which is sealed against the cervix to prevent the fluid from leaking back.
Semen is lost at various steps of the operation. Some semen is left behind in the storage straw when it is mixed with the diluting fluid in the ampule. Some semen is also left behind in the ampule when the semen mixed with diluting fluid is aspirated into the pipette. And finally, some semen is left behind in the pipette when the semen mixed with diluting fluid and loaded in the pipette is pushed with air out of the pipette.
These losses of semen produce an inseminating fluid charge with a low sperm concentration and a corresponding low fertilization success rate. In addition, the total charge of semen and diluting fluid cannot be readily adjusted to accomodate the various size cervixes and uteruses found among animals of different sizes, breeds and species. Thus an insemination device with an improved ability of delivering an optimum quantity and concentration of semen, and that lends itself to delivering an optimum total charge of semen and diluting fluid, is desirable.